1. Field of the Invention
The present invention relates to a petroleum well for producing petroleum products. In one aspect, the present invention relates to systems and methods for monitoring fluid flow during petroleum production by controllably injecting tracer materials into at least one fluid flow stream with at least one electrically controllable downhole tracer injection system of a petroleum well.
2. Description of Related Art
The controlled injection of materials into petroleum wells (i.e., oil and gas wells) is an established practice frequently used to increase recovery, or to analyze production conditions.
It is useful to distinguish between types of injection, depending on the quantities of materials that will be injected. Large volumes of injected materials are injected into formations to displace formation fluids towards producing wells. The most common example is water flooding.
In a less extreme case, materials are introduced downhole into a well to effect treatment within the well. Examples of these treatments include: (1) foaming agents to improve the efficiency of artificial lift; (2) paraffin solvents to prevent deposition of solids onto the tubing; and (3) surfactants to improve the flow characteristics of produced fluids. These types of treatment entail modification of the well fluids themselves. Smaller quantities are needed, yet these types of injection are typically supplied by additional tubing routed downhole from the surface.
Still other applications require even smaller quantities of materials to be injected, such as: (1) corrosion inhibitors to prevent or reduce corrosion of well equipment; (2) scale preventers to prevent or reduce scaling of well equipment; and (3) tracer materials to monitor the flow characteristics of various well sections. In these cases the quantities required are small enough that the materials may be supplied from a downhole reservoir, avoiding the need to run supply tubing downhole from the surface. However, the successful application of techniques requiring controlled injection from a downhole reservoir requires that means must be provided to power and communicate with the injection equipment downhole. In existing practice this requires the use of electrical cables running from the surface to the injection modules at depth in the well. Such cables are expensive and not completely reliable, and as a consequence are considered undesirable in current production practice.
The use of tracers to identify materials and track their flow is an established technique in other industries, and the development of the tracer materials and the detectors has proceeded to the point where the materials may be sensed in dilutions down to 10−10, and millions of individually identifiable taggants are available. A representative leading supplier of such materials and detection equipment is Isotag LLC of Houston, Tex.
The use of tracers to determine flow patterns has been applied in a wide variety of research fields, such as observing biological circulatory systems in animals and plants. It has also been offered as a commercial service in the oilfield, for instance as a means to analyze injection profiles. However the use of tracers for production in the oilfield is by exception, since existing methods require the insertion into the borehole of special equipment powered and controlled using cables or hydraulic lines from the surface to depth in the well.
All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes, and indicative of the knowledge of one of ordinary skill in the art.